Chemistry
Experimental Chemistry 1 Experimental Chemistry 2 Kinetic Particle Theory Atomic Structure Chemical Bonds Ionic & Covalent Compounds Ionic Compounds (Giant Crystal Lattice) *Ionic Compound consists of positively-charged ions of metals and negatively charged ions of non-metals reguarly arranged in a giant crystal lattice. *These oppositely charged ions are held together by strong electrostatic forces of attraction (ionic bonds) *Example: Sodium Chloride, Magnesium Oxide *Physical Property: **High melting and boiling point as a large amount of energy is required to overcome the strong electrostatic forces of attration between the ions. **Usually solid at room temperature. **Soluble in water and insoluble in organic solvents (chloroform and petrol). **Do not conduct electricity in solid state (ions are held in fixed position) but in molten/liquid state (ions are free to move). Covalent Compounds *Simple Molecular and Giant Covalent *Example: Carbon Dioxide, Methane, Ammonia, Water Simple Molecular Structures ''' *Consists of small covalent molecules with '''weak forces of attraction between molecules Physical Properties: *Low melting and boiling point as little energy is need to overcome the weak forces of attraction between molecules. *Insoluble in water and soluble in inorganic solvents. *'Cannot conduct electricity in any states' as molecules are electrically neutral and have no free-moving ions. Giant Molecular Structuces *Large molecule containing thousands or millions of atoms covalently bonded together. *Exist as a giant. three-dimensional molecular structures. *Examples: Diamond, Graphite, Silicon and Silicon Dioxide. Relative Masses of Atoms & Molecules Mole Concept Empirical and Molecular Formula Acids & Bases Definition of Acid: A substance which gives H+ ions as the only positive ions when dissolved in water. '''(Only behaves as acids in aqueous state) '''Physical properties: *Sour taste *Hazardous & corrosive *Turns damp BLUE '''litmus paper '''RED *Has a pH value of less than 7 *Dissolves in water to form solutions which can conduct electricity Chemical properties: *Acids react with reactive metals (Mg, Zn, Fe) to form salt & hydrogen gas *Acids react with metal carbonates to form salt, water & carbon dioxide gas *Acids react with bases (metal oxides/hydroxides) '''to form salt & water '''Basicity of Acids: Maximum number of H+ ions produced by a molecule of an acid. ' ' Monobasic: '''HCl(aq) --> '''H+(aq) + Cl-(aq) Dibasic: '''H2SO4(aq) --> '''2H+(aq) + SO42-(aq) Tribasic: '''H3PO4(aq) --> '''3H+(aq) + PO43-(aq) ' ' Strength of Acid: Refers to the extent of ionization when an acid is dissolved in water. ' ' ' ' ' ' ' ' Concentration of Acid: The amount of acid dissolved in 1dm3 of water '''(g or mol per dm3) '''Uses of Acids: *'Hydrochloric Acid(HCl): '''Removes rust from metals. *'Nitric Acid(HNO3): Making of explosives. *'Sulfuric Acid(H2SO4): '''Making of fertilizers. *'Ethanoic Acid(CH3COOH): 'Preservation of food. '''Definition of Bases: Bases are oxides and hydroxides of metals which react with acid to produce salt & water. '(Oxides and Hydroxides are soluble in water) ' ' 'Definition of Alkali: A substance that gives off OH- ions as the only negative ions when dissolved in water. '(Alkalis are soluble bases) '''Physical properties: *Bitter taste *Feels soapy *Hazardous & corrosive *Turns damp RED litmus paper BLUE *Has a pH value greater than 7 *Dissolves in water to form solutions that conduct electricity Chemical properties: *Alkalis react with acids to form salt and water *Alkalis (except aqueous NH3) '''react with ammonium compounds to form salt, water & ammonia gas *Alkalis react with solutions of metal ions to form '''INSOLUBLE '''metal hydroxides '''3NaOH(aq) + FeCl3(aq) --> 3NaCl(aq) + Fe(OH)3(s) ' ' ' ' Uses of Alkalis: ' To neutralise acids:' *Toothpaste contains Mg(OH)2, which neutralises acids in the mouth. *'Mg(OH)2' (Milk of Magnesia) is consumed by patients to neutralise excess acid in their stomachs. *'CaO '(lime) and Ca(OH)2 (slaked lime) are used to neutralise acid soil. To dissolve dirt & grease: *Soap and detergents are milk alkalis. Ammonia is used in liquids for cleaning glass windows. *Floor cleaners often contain NaOH. ' ' Test for Carbon Dioxide gas: *Bubble gas into test tube of lime water. *When white precipitate forms in the limewater, carbon dioxide is present. Test for Hydrogen gas: *Place a burning splint at the mouth of the test tube. *If the burning splint extinguishes with a ‘pop’ sound, hydrogen gas is present. Test for Ammonia gas: *Place a damp red litmus paper at the mouth of the test tube. *If the red litmus paper turns blue, ammonia gas is present. Salts Chemical Analysis (Qualitative) Periodic Table Patterns in the Periodic Table *Elements in the Periodic Table are arranged in order of proton (atomic) number, which increases from left to right across the table. *''Horizontal'' rows of elements in the Table are called Period. **Each member in the same period has the same number of electron shells. *''V''ertical 'columns of elements in the Table are called '''Group. (roman numerals, i.e. Group VII) **Elements in the same group have the same number of valence electron'''s (same as group number) **Hence they have '''similiar chemical properties, form ions with same charge, form same number of bonds and form compounds with similar formulas. Group Properties Group I Elements (Alkali Metals) *Lithium (Li+), Sodium (Na+), Potassium (K+), Rubidium (Rb+), Caesium (Cs+) *Physical Properties **'Soft, shiny, silvery' solids which rapidly tarnish (dullness of colour, loss of brightness) in air. **Loses electrons to form cations. **Colour gets darker down the group. **Melting point decreases down the group. **Density increases down the group. **Compounds of alkali metals are white and they dissolve in water to form colourless solutions. **eg. Sodium Chloride dissolve in water to form colourless salt solution) *Chemical Properties **'Very reactive metals', thus need to be stored under oil. **Reacts with water to form alkali and hydrogen gas. **Eg: 2 Na (s) + 2 H20 -> 2 NaOH (aq) + H2 (g) **Reactivity increases down the group. **As atomic size increases down the group, the electrostatic forces of attraction between the nucleus and the outermost electrons decreases. Thus the readiness to lose electrons increases down the group, leading to greater reactivity. Group VII Elements (Halogens) *A group of''' very reactive non-metals'. *Called 'Halogens' (salt formers) because '''they react with most metals to form salts'. *Consists of small covalently bonded molecules. Each molecule contains two atoms and is described as being diatomic molecules. *Physical Properties *Iodine is black when solid, brown when aqueous and violet when gaseous. '' *Melting and boiling point increases down the group. *All halogens are '''coloured and colour intensity increases down the group'. *Chemical Properties **Reactivity of halogens decreases down the group. **As atomic size of the elements increases down the group, electrostatic forces of attraction between the nucleus and outermost (valence) electrons decreases. Thus, the ability to attract electrons decreases down the group, leading to decreasing reactivity with other substances. **Undergoes displacement reaction ***Reaction in which a more reactive halogen takes the place of a less reactive halogen halogen from its salt. ***Eg. Chlorine + Potassium Iodide --> Potassium Chloride + Iodine ***2 Cl2 + 2 KI --> 2 KCl2 + I2 ***Observation: colourless solution turns brown. ***Explanation: As chlorine is more reactive ''than iodine, it displaces iodine from its salt solution (potassium iodide) to form potassium chloride and iodine. The solution turns from colourless to brown due to the presence of iodine. Group 0 Elements (Noble Gas) *Physical Properties **They are the least reactive non-metals. ''Chemically inert. **Are all colourless at room temperature. **Consists of single atoms and are said to be monoatomic. **'Unreactive: ''The atom has a full/complete valence shell of electrons. ' **Said to have a stable duplet or octet structure. **Melting and boiling point increases down the group. **'Insoluble in water'. *Uses of noble gases **Helium: To fill balloons and inflat aircraft tyres. (Low density) **Argon: To fill electric light bulbs and used in arc welding of stainless steel **Neon: To fill advertising strip light Ammonia Air and the Atmosphere Redox Reactions Redox reactions occur when both reduction and oxidation takes place at the same time. *Oxidation *#Gain of oxygen *#Loss of hydrogen *#Loss of electrons *#Increase in oxidation state *Reduction *#Loss of oxygen *#Gain of hydrogen *#Gain of electrons *#Decrease in oxidation state *In a chemical reaction, a substance which brings reduction in another substance is called a reducing agent, it then gets oxidised. Whereas a substance which brings about oxidation in another substance is called an oxidation agent, it then get reduced. *Redox reaction in terms of oxygen gain/loss **Example: CuO (s) + H2 (g) -> Cu (s) + H2O (I) ***H2 is oxidised because H2 gains oxygen to form H2O. ***CuO is reduced because CuO loses oxygen to form Cu. ***H2 is the reducing agent because it removes oxygen from CuO and causes CuO to be reduced. ***CuO is the oxidising agent because it gives oxygen to H2 and causes H2 to be oxidised. *Redox reaction in terms of hydrogen gain/loss **Example: H2S (g) + Cl2 (g) -> 2HCl (g) + S (s) ***H2S is oxidised as it loses hydrogen to form S. ***Cl2 is reduced as it gains hydrogen to form HCl. ***H2S is the reducing agent because it gives hydrogen to Cl2 and causes it to be reduced. ***Cl2 is the oxidising agent because it removes hydrogen from H2S and causes it to be oxidised. *Redox reaction in terms of electron transfe **Example: Mg (s) + 2HCl (aq) -> MgCl2 (aq) + H2 (g) ***Mg is oxidised as Mg loses electrons to form Mg2+ in MgCl2. ***HCl is reduced because the H+ ions gains electrons to form H2. ***HCl is the oxidising agent while Mg is the reducing agent. *Oxidation state (number) **An arbitary number assigned to an element in a compound to indicate the state of the element. (The charge of an atom would have if it existed as an ion) **table here thank you! *Redox reactions in terms of changes in oxidation state **Example: Fe (s) + CuSO4 (aq) -> FeSO4 (aq) + Cu (s) ***Fe is oxidised as the oxidation state increases from 0 in Fe to +2 in FeSO4. ***CuSO4 is reduced as the oxidation decreases from +2 in CuSO4 to in Cu. ***Reducing agent: Fe / Oxidising agent: CuSO4 *Examples of non-redox reaction **Heating of metal carbonates (CaCO3 -> CaO + CO2) **Neutralisation (H+ + OH- -> H2O) **Precipitation (Ag+ + Cl- -> AgCl) **Acid + Carbonate (H2SO4 + MgCO3 -> MgSO4 + H2O) *Test for reducing agent & oxidising agent **table here thank you! Energy from Chemicals (Exothermic & Endothermic) Speed of Reaction The rate of reaction is the change in amount or concentration of a reactant/product per unit time. *Ways of measuring rate of reaction **A change in volume of gas given off **A change in mass during reaction **Formation of precipitate **Dissolving of a solid *Factors affecting rate of reaction **Concentration ***A more concentrated solution contains more reactant particles per volume, frequency of effective collision increases, therefore increasing the rate of reaction. **Surface Area (only applicable for solid) ***A powered solid reactant has a larger surface area than particles of the same mass. Thus when area of contact between powdered reactant and solution increases, frequency of effective collision increases, therefore increasing the rate of reaction. **Temperature ***At higher temperature, reacting particles gain has a higher amount of kinetic energy, moving faster and colliding more frequently. Thus, when more reacting particles have energy equal or greater than the activation energy of the reaction, frequency of effective collision increases, therefore increasing the rate of reaction. **Pressure (only applicable for gases) ***At a higher pressure, number of particles per unit volume. Thus, frequency of effective collison increases, therefore increasing the rate of reaction. **Catalyst ***A substance which increases the rate of reaction with itself reamining chemically unchanged after the reaction. (Thus does not appear in chemical equations) ***Provides an alternative pathway that has a lower activation energy than original for the reaction to proceed. ***Thus, when increasing the number of particles that have energy equal or greater than activation energy, frequency of effective collision increases, therefore increasing the rate of reaction. Organic Chemistry: Alkanes Alkanes: General formula: CnH2n+2 Saturated hydrocarbon as all carbon atoms within the hydrocarbon is used to from covalent bonds with 4 other atoms. Physicals properties: - M.P. & B.P. increases down the group -> As the size of the molecules increases down the homologous series, the number of covalent bonds required to be broken down for a change of state increases. Therefore M.P. and B.P. increases down the group; directly proportional to number of covalent bonds within the molecule. - Viscosity increases down the group -> Stronger intermolecular forces attraction between the alkane molecules increases due the increase in relative molecular mass of the alkanes molecules. - Insoluble in water, soluble in organic solvents. - Flammability of alkanes decrease down the homologous series. Flammability is dependent on boiling point of the alkanes. As the boiling point deceases, it is easier to ignite the alkane. Chemical properties of alkanes: Alkanes burn in excess oxygen to form carbon dioxide/ + water Combustion of alkanes in insufficient oxygen, carbon monoxide and/or soot + water are formed. Excess oxygen: C3H8 + 7O2 -> 3CO2 + 4H2O Insufficient oxygen: 2C3H8 + 7O2 -> 6CO + 4H2O (carbon monoxide formed) C3H8 + 2O2 -> 3C + 4H2O (soot is formed in place of carbon dioxide) Substitution reaction of alkanes: - Alkanes react with halogens (F, Cl, Br) in presence of ultraviolet light. - Known as photochemical reaction. - Iodine is relatively unreactive towards alkanes. - Rate of reaction with halogen decreases down the halogen homologous series. (Cl is more reactive compared to Br) - Atom or functional group is replaced by an atom of a halogen Isomerism: Isomers are compounds that have the same molecular formula but different structural formula. - Different isomers of the same compound have different boiling points. (Different number of covalent bonding between atoms) - Number of isomers increase with number of carbon atoms in compound. - Isomers of alkanes have a methyl group: -CH3 - Naming is in terms of presence of methyl group on the numerical order of carbons atoms regardless of orientation. E.g. 2-methylpropane & 2,2-methylpropane. Organic Chemistry: Alkenes Alkenes: General formula: CnH2n Unsaturated hydrocarbons as each carbon atom in the alkene is not bonded to 4 other atoms. (Presence of C=C double bonds) Alkenes are acquired from the cracking of petroleum. (At least 1 product is an alkene) Catalytic cracking: - Petroleum fraction is vaporised (gaseous form). - Gaseous petroleum fraction is passed over a heated solid catalyst. - A mixture of short-chained hydrocarbons is produced. Steam cracking: - Petroleum fraction (Naphtha) is mixed with steam and heated briefly. - A mixture of short-chained molecules is produced. Alkenes combust in excess oxygen to produce water and carbon dioxide. When burnt in insufficient oxygen, carbon monoxide/soot + water is produced. **Important concept to take note of** Ethene (C2H4) burns with a sootier flame as compared to ethane (C2H6). This is because alkenes have a higher carbon composition by mass as compared to alkanes. -> ethene: 85.7% whereas ethane: 80% Addition reactions: An addition reaction is one in which two or more molecules react to form a single product. Addition of Hydrogen(Hydrogenation): Alkenes undergo addition of hydrogen to form alkanes. Ethene + Hydrogen -(nickel catalyst)> Ethane C2H4 + H2 -(nickel catalyst)> C2H6 Manufacture of margarine: Polyunsaturated vegetable oil contains many carbon-carbon double bonds(Insufficient energy present to break intermolecular forces of attraction for vegetable oil to be a gas at room temperature. Therefore vegetable oil is a liquid at room temperature). Some carbon atoms which are double bonded together undergo addition of hydrogen to form solid margarine in room temperature. **Addition of hydrogen increases the mass and intermolecular forces of attraction between molecules of margarine(strength of intermolecular forces of attraction directly proportional to mass of the molecules) As the strength of intermolecular forces between molecules increase, the energy required to overcome the forces increases. Since there is insufficient energy in the surroundings to overcome these intermolecular forces of attractions, and hence melting point. Therefore, margarine molecules take solid state arrangement. Addition of Water(Hydration): Alkenes react with steam to form alcohol. Ethene + Steam <(hot phosphoric(V)acid as catalyst, 300ºC, 65atm)> Ethanol C2H4 + H2O <(hot phosphoric(V)acid, 300ºC, 65atm)> C2H5OH *Note that reaction is reversible. Addition of Bromine(Bromination): Bromine reacts with alkenes in an addition reaction. Bromine molecule adds to the C=C double bonds in alkene molecules. One bromine ion combines with each carbon atom of the C=C double bond. Ethene + Bromine -> 1,2-dibromoethene Test for presence of unsaturated compounds: Addition of an alkene will rapidly decolourise reddish-brown aqueous bromine. *Note: Copper solid is reddish-brown/pink as well. For liquids: Add aqueous bromine to the compound and shake. For gases: Bubble gas through aqueous bromine. Observation: Reddish-brown aqueous bromine will decolourise rapidly (If an unsaturated compound is present.) Isomers of Alkenes: The double bonding is found in different positions of the alkene molecule. Organic Chemistry: Alcohols Alcohols: General formula: CnH(2n+1)OH Functional group: -OH (hydroxyl group) Physical properties: - Colourless liquids. - Low boiling points. - Soluble in water. - As number of carbon atoms increase in a molecule, the boiling points of the alcohols increase but the solubility in water decreases. **Key concept** When a substance dissolves in a solvent, the dissolved substances fill up the spaces between particles of the solvent. As the size of the solute's particles increase, it is more difficult for the solute's particles to squeeze in the spaces between the solvent's particles. Therefore the solubility of a substance decreases as the size of the molecule increases. When drawing non-full structural formula of any alcohol, the O from -OH must be linked to C. Manufacture of Ethanol: (Industrial method) Steam + Ethene -(hot phosphoric(V)acid as catalyst, 300ºC, 65atm)> Ethanol H20 + C2H4 -(hot phophoric(V)acid, 300)C, 65atm)> C2H5OH *Note that reaction is reversible Process of manufacture: Ethene + Steam(Reactants) > Heater > Reactor(300ºC, 65atm, catalyst) > Condenser > Ethanol + Water(Products) **Unreacted Ethene and Steam is redirected back to the heater for another round of reaction to increase efficiency. (Efficiency = Output mass/Input mass x 100%) Fermentation of Sugars: Chemical reaction in which sugars are broken down into smaller molecules by microorganisms. Glucose -(yeast, absence of oxygen, 37ºC)> Ethanol + Carbon dioxide C6H12O6 -(yeast + absence of oxygen, 37ºC)> C2H5OH + CO2 Maximum output of yeast is 15%, after which the yeast will die and the reaction stops. Ethanol is separated from the mixture by fractional distillation. Uses: - Ethanol is used as a solvent for perfumes, varnishes and deodorants. (Alcohol has a low boiling point and evaporates easily) - A constituent for alcholic drinks. - Used as fuel for vehicles Combustion of Alcohol: Alcohol + Oxygen -> Water + Carbon dioxide E.g. Ethanol + Oxygen -> Water + Carbon dioxide C2H5OH + 3O2 -> 3H20 + 2CO2 Oxidation of Alcohol: Alcohol + Oxygen -(bacteria)> Carboxylic acid + Water E.g. Ethanol + Oxygen -(bacteria)> Ethanoic acid + Water C2H5OH + O2 -(bacteria)> C2H5COOH + H2O ------------------ Oxygen derived from atmospheric air. Alcohol + Oxygen -> Carboxylic acid + Water E.g. Ethanol + Oxygen -> Ethanoic acid + Water C2H5OH + O2 -> C2H5COOH + H2O ------------------ Oxygen derived from oxidising agent e.g. acidified potassium manganate(VII). Organic Chemistry: Carboxylic Acids & Esters Carboxylic Acids: General formula: CnH(2n+1)COOH Functional group: -COOH (carboxyl group) Chemical properties: - Are weak monobasic acids. - Undergo reactions typical of acids. Reacts with metals to form salt + hydrogen gas Reacts with metal carbonates to form salt + water + carbon dioxide Reacts with alkalis to form salt + water Preparation of ethanoic acid: Oxidation of Alcohol: Alcohol + Oxygen -(bacteria)> Carboxylic acid + Water E.g. Ethanol + Oxygen -(bacteria)> Ethanoic acid + Water C2H5OH + O2 -(bacteria)> C2H5COOH + H2O ------------------ Oxygen derived from atmospheric air. Alcohol + Oxygen -> Carboxylic acid + Water E.g. Ethanol + Oxygen -> Ethanoic acid + Water C2H5OH + O2 -> C2H5COOH + H2O ------------------ Oxygen derived from oxidising agent e.g. acidified potassium manganate(VII). The setup consists of a condenser which takes up similar functions as the fractionating column. To prevent ethane and intermediate products from escaping before the acids is formed. Oxidation of Methane: Methane + Oxygen -(catalysts)> Ethanoic acid + Water CH4 + O2 -(catalysts)> CH3COOH + H2O Esterification: Carboxylic acid + Alchohol -(concentrated sulfuric acid)> Ester + Water E.g. Ethanoic acid + Methanol -(concentrated sulfuric acid)> Methylethanoate + Water CH3COOH + CH3OH -(concentrated sulfuric acid)> CH3COOCH3 + H2O bond formed is called an ester linkage Naming of esters: Alcohol portion then acid portion. For chemical formula, acid first followed by alcohol.) -thyl (from alcohol) + -oate (from carboxylic acid) Esters are isomers of carboxylic acids. E.g. C3H6O2: CH3COOCH3, HCOOC2H5, C2H5COOH Methylethanoate, Ethylmethanoate, Propanoic acid. Uses of esters: - Solvent - Fragrances (Perfume/deodorant) - Artificial flavourings Organic Chemistry: Macromolecules Macromolecules A macromolecule is a large molecule made up of a large number of atoms held together by covalent bonds. -> Process is called polymerisation. Organic macromolecules: Synthetic - Plastics Natural - Proteins, Fats & Haemoglobin Polymerisation is a reaction in which many small molecules are joint together to form a large molecule. Monomer - A small molecule that can be joint together with other similar molecules to form one big molecule. Polymer - A long-chained macromolecule formed by joining together many small molecules (monomers) Repeating unit(s): The smallest part of a polymer which, when repeated many times, form the whole polymer. Addition Polymerisation: A reaction in which many small molecules are joined to form one molecule as the only product. Monomers that undergo addition polymerisation are unsaturated (Double/triple bonding) Uses of Poly(ethene): - Plastic bags - Cling film - Flexible water pipes - Flexible bottles Other plastics formed by addition polymerisation + uses: Poly(chloroethene)/Polyvinyl chloride/PVC: For water pipes; waterproof plastic sheeting; insulating for electric cables and wires. Poly(phenylethene)/polystyrene: For packaging and containers for electrical goods disposable cups and food containers used in 'fast food' restaurants and hawker centres. Perspex: Used for making plastic windows and to make models of machines and buildings as it is transparent and does not break as easily as glass. Poly(tetrafluoroethene): Used to coat 'non-stick' pots and pans as it is chemically inert, heat-resistant and repels water. Condensation Polymerisation: A reaction in which small molecules join together to form large molecules with the elimination of a small molecule. (Usually water) Nylon: NH3-[|||]-NH3 + HOOC- -COOH -> -NH-[|||]-NHCO- -CO- Amine group + Acid group -> Polyamide (with amide linkage NHCO) Uses of Nylon: - To make cloth - Raincoats - Parachutes - Fishing lines Terylene: HO- -OH + HOOC-[|||]-COOH -> H2O + -O- -OOC-[|||]-COO- Alcohol group + Acid group -> Water + Polyester (with ester linkage COO) Uses of Terylene: - For polyester clothing - Making curtain materials Advantages of using plastics: - Lightweight - Durable - Easy to work with (Can be moulded and shaped) Pollution problems caused by disposal of plastics: Burning: Burning of plastics produce poisonous gases such as carbon monoxide. PVC produces hydrogen chloride and dioxins(carcinogens), while nylon produces hydrogen cynide(extreme toxicity) and nitrogen oxides(acid rain) Landfill: Plastics are non-biodegradable. They cannot be broken down naturally by bacteria in the ground. This will cause accumulation of plastic waste and a long-term litter problem. Plastics can also kill animals when ingested. Organic Chemistry: Crude Oil & Petroleum Fuels & Crude Oil: Fuel: A substance that releases energy when burnt. Fossil Fuel: are formed from the remains of dead plants and animals. Examples of fossil fuels: - Natural gas (mainly methane CH4) - Petroleum - Coal Natural Gas: - Produced by anaerobic decay of organic matter. - Can be found together with petroleum or in gas fields. - Contains mainly methane (CH4) - Needs to be processed to remove impurities such as sulfur & ethane, before it can be used as fuel. Petroleum: (Crude oil) - Produced by anaerobic decay of organic matter. - Contains a mixture of hydrocarbons. - It has to be separated into different products and fuels to be used. FRACTIONAL DISTILLATION OF PETROLEUM: - Petroleum is heated and evaporates. The vapour is passed into a fractional distillation column. - The column is cooler at the top than at the bottom. As the vapour rises up the column, they cool. - Hydrocarbons with lower boiling points remain as vapour and move up the the distillation column. - Hydrocarbons with higher boiling points come into contact with the liquid and then condense. - Heat is released as the vapour condenses. - The heat released causes the liquids with lower boiling points to evaporate and move up higher in the distillation column. - The condensates condense at different temperatures. Therefore they are collected at different heights, depending on their boiling ranges. - The fraction with the lowest boiling range condenses and will be collected at the top of the fractionating column, while those with the highest boiling range condense at the bottom. **Each fraction is a mixture of hydrocarbons which boil over a range of temperatures. Fractions of petroleum: Petroleum Gas ----- Fuel for cooking Petrol --------------- Fuel for motor cars Naphtha ------------- Chemical feedstock for alcohol, plastics and drugs, etc. Kerosene ------------ Fuel for aircraft and for heating & cooking Diesel Oil ----------- Fuel for diesel engines Lubricating Oil ----- Lubricants for machines, also for waxes & polishes Bitumen ------------- Tar for surfacing roads Competing uses of petroleum: - Petroleum is used as a fuel and a chemical feedstock. - If more petroleum is used as fuel, there will be less available for producing these chemicals. - A shortage of petroleum will lead to a shortage of chemicals as well. - Alternative sources of energy will need to be found to replace petroleum as fuel. Metals